Next thing, I suppose, is to figure out how to tuft-test the whole back of the car. I saw a GM SUV on the highway a while back (maybe a Buick Enclave?) and it was pretty clear from the pattern of dirt on the tailgate that there was a donut-shaped vortex behind the car. That seems like a good way to extend the effective taper of the rear of the vehicle. Sounds like it's time to spend an evening with Hucho's book.
